To make the vinaigrette, stir together vinegar, mustard and garlic in small bowl. Add a good pinch of salt and pepper, then whisk in olive oil. Taste for seasoning, then set aside.

Shuck and cook the fresh shelling beans by simmering in lightly salted water to cover. They should be tender in about 30 minutes. Let shelling beans cool in their cooking water. (May be cooked ahead.)

Cook the green beans, romano beans and wax beans separately. Simmer each type in lightly salted water for 3 to 5 minutes, until just tender. Spread them out on plates to cool to room temperature.

Heat a dry cast-iron skillet over medium-high heat. Lay onion slices in the skillet and let them char and soften slightly on one side, about 5 minutes. Turn and char the other side. Set aside to cool. Toast marjoram on the hot skillet until it chars slightly, about one minute, then remove. (You may char the onions and marjoram on an outdoor grill or under the broiler.)

To assemble the salad, drain the shell beans and put them in a large serving bowl. Add cooked green beans and charred onions. Season with salt and pepper. Add vinaigrette and toss well. Crumble marjoram and sprinkle over salad. Sprinkle with parsley and serve.